The present invention relates to audio and video signal processing, and more particularly relates to the processing of such signals to embed auxiliary data (e.g. identification or control data therein), and the subsequent extraction and use of such data.
In accordance with an illustrative embodiment of the present invention, an input content signal-representing audio or videoxe2x80x94is steganographically encoded to hide plural-bit auxiliary data therein. The encoding operation changes over time, e.g., by using different xe2x80x9ckeyxe2x80x9d data for successive portions of the content signal. In some embodiments, the key data used in one portion of the signal is a function of auxiliary data decoded from a preceding portion. Consequently, to successfully decode the auxiliary data, the decoder must have successfully decoded a previous portion. In essence, decoding instructions are sent xe2x80x9con the flyxe2x80x9d in such embodiments.
In some embodiments, the auxiliary data is changed in temporally adjoining portions of the content signalxe2x80x94e.g., in successive frames of video or blocks of audio. In other embodiments, the key is changed less frequently, e.g., on a daily basis. External events may also trigger changing of the key data.
The foregoing and additional features and advantages of the present invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings.